Showing papers by "Xiaoding Wei published in 2009"
TL;DR: In this article, a thermodynamically rigorous continuum description of the elastic response is formulated by expanding the elastic strain energy density in a Taylor series in strain truncated after the fifth-order term.
Abstract: The nonlinear in-plane elastic properties of graphene are calculated using density-functional theory. A thermodynamically rigorous continuum description of the elastic response is formulated by expanding the elastic strain energy density in a Taylor series in strain truncated after the fifth-order term. Upon accounting for the symmetries of graphene, a total of fourteen nonzero independent elastic constants are determined by least-squares fit to the ab initio calculations. The nonlinear continuum description is valid for infinitesimal and finite strains under arbitrary in-plane tensile loading in circumstance for which the bending stiffness can be neglected. The continuum formulation is suitable for incorporation into the finite element method.
392 citations
TL;DR: In this article, the elastic properties and frictional properties of graphene samples of varying thickness using an atomic force microscope were investigated for tensile testing, and it was shown that the frictional force between an AFM tip and graphene decreases with thickness for samples from 1 to 4 layers, and does not depend on the presence of a substrate.
Abstract: We descnbe studies of the elastic properties and frictional characteristics of graphene samples of varying thickness using an atomic force microscope. For tensile testing, graphene is suspended over micron-sized circular holes and indented by atomic force microscope (AFM) tips. Fitting of the force-displacement curves yields the prestress and elastic stiffness, while comparison of the breaking force to simulation gives the ultimate strength, which is the highest measured for any material. Experiments on samples with 1-3 atomic layers yield similar values for the intrinsic stiffness and strength of a single sheet, but also reveal differences in mechanical behavior with thickness. The frictional force between an AFM tip and graphene decreases with thickness for samples from 1 to 4 layers, and does not depend on the presence of a substrate. High-resolution friction force imaging in stick-slip mode shows the same trend, and allows direct imaging of the crystal lattice.
360 citations
Patent•
06 Aug 2009
TL;DR: In this article, a deformable sheet membrane can be configured to include a specified integer number of one or more monolayers, and a storage medium can comprise information about the suspended membrane or the substrate that, with a deflection displacement response of the suspension membrane to an applied force or pressure, provides a measurement of the applied force and pressure.
Abstract: Force, pressure, or stiffness measurement or calibration can be provided, such as by using a graphene or other sheet membrane, which can provide a specified number of monolayers suspended over a substantially circular well. In an example, the apparatus can include a substrate, including a substantially circular well. A deformable sheet membrane can be suspended over the well. The membrane can be configured to include a specified integer number of one or more monolayers. A storage medium can comprise accompanying information about the suspended membrane or the substrate that, with a deflection displacement response of the suspended membrane to an applied force or pressure, provides a measurement of the applied force or pressure.
7 citations